The current work represents a continuation of the investigation of biochemical function in relation to fine structural elements studied by combining biochemistry, cytochemistry and electron microscopy techniques. The work covers several areas now in progress, which are natural extensions of the current themes. These include: (1) Studies on membrane biogenesis including the endoplasmic reticulum of hepatocytes and the plasma membrane of the salt gland. The enzymes being studied relate to phospholipid synthesis for both systems, drug detoxifying enzymes for the ER and Na/K ATPase for the salt gland. (2) Continued studies on the nervous system with special reference to adenyl cyclase and choline acetylase. Method for localizing latter enzyme shall be used in studies to examine the site of origin of clear synaptic vesicles at cholinergic ending. (3) Studies of membrane composition in relation to fine structure involved in the used of newly synthesized reagents for the localization of specific lipids or cholesterol and of groups in proteins. (4) Finally, studies on isolated capillary endothelium will continue with reference to understanding the enzymatic components in relation to function as well as the phenomenon to the mechanism of micropinocytosis. An attempt will be made to isolate micropinocytic invagination and vesicles, and to biochemically and cytochemically characterize them.